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Ex situ seed banks provide an effective conservation and utilization system for crops and their wild relatives. Efforts are made to reduce genetic drift in conservation, where regeneration is a critical step. In the present study, we examined eight wild populations of red clover (Trifolium pratense L.) according to 13 morphological and phenological traits. Samples of original collected seed were grown and compared with plants from first and second ex situ generation, with commercial cultivars and landraces being included for purposes of comparison. Variance analysis and Tukey multiple comparisons of means showed that the commercial cultivars and landraces were clearly distinct from the wild populations and were excluded from the further analysis. Despite the fact that the wild accessions were collected from a geographically delimited region in Norway, they exhibited significant differences in several of the measured traits. The main phenotypic patterns remain after ex situ regenerations. However, the mean values for four of the examined traits (across accessions) did change significantly from one generation to the next. Two of the eight accessions had significantly changed from one generation to the next, a tendency was observed across all the studied traits. The results were discussed in terms of regeneration circumstances. Observed changes appeared to be directional, going from populations with predominantly wild morphological types towards plants more closely resembling the commercial cultivars. Such a directional change implies that selection or gene flow has been acting on the accessions during regeneration, rather than random changes owing to genetic drift.

Drought remains the most important factor that affects rice productivity, especially in rainfed areas, worldwide. Upland rice is one of the crop choices of farmers in the rainfed environment. Although upland rice varieties require less water than lowland rice varieties, yields often remain limited by drought, particularly in the period of early growth. The aims of this study were to identify the traits related to early drought tolerance in upland rice varieties, and to identify the potential sources of germplasm for early drought tolerance. A total of sixty upland rice varieties were planted in a factorial experiment with a randomized complete block design with 3 replications in the rainy seasons of 2011 and 2012, under greenhouse conditions. Based on the drought tolerance index (DTI), the test germplasm sources were classified into three groups: (i) susceptible; (ii) moderately tolerant; (iii) tolerant to drought stress. Grain yield (GY) showed significant negative correlations with the leaf rolling score (r= − 0.623, P< 0.01), the leaf death score (LDS) (r= − 0.673, P< 0.01) and the recovery score (r= − 0.746, P< 0.01), while leaf dry matter (r= 0.698, P< 0.01) and leaf water potential (r= 0.618, P< 0.01) had significant positive correlations with GY. These findings indicate the suitability of the DTI as the selection criteria for early drought tolerance in a breeding programme. In addition, the upland rice germplasm accessions KKU-ULR011, KKU-ULR012, KKU-ULR125, KKU-ULR199 and KKU-ULR292 were identified as having high levels of stability for drought tolerance in both the 2011 and 2012 experiments, suggesting their potential for further use for rice variety improvement for drought tolerance.

Knowledge on genetic diversity is necessary to determine the relationships among the genotypes, which allow the selection of individual accessions for crop breeding programmes. The present study aimed at assessing the extent and pattern of genetic diversity within a set of 251 sorghum genotypes using SSR markers. A total of 393 alleles were detected from the 251 genotypes, with the number of alleles ranging from 2 (Xcup11) to 24 (Sb5-206) and an average of 10.07 alleles per primer pair. Pairwise Wright's FST statistic and Nei's genetic distance estimates revealed that the race and geographical origin were responsible for the pattern of diversity and structure in the genetic materials. In addition, the analysis also revealed high genetic differentiation between the rainy and post-rainy sorghum groups. Narrow diversity was observed among the different working groups in the rainy (restorers and varieties) and post-rainy (varieties and advanced breeding lines) sorghum groups. Neighbour-joining and STRUCTURE analysis also classified 44 elite lines broadly into two distinct groups (rainy and post-rainy). However, limited diversity within the rainy and post-rainy sorghum groups warranted an urgent need for the utilization of diverse germplasm accessions for broadening the genetic base of the Indian breeding programme. The diverse germplasm accessions identified from the mini-core accessions for utilization in breeding programmes are discussed.

Cassava germplasm collection is important for the preservation of genetic variability, allowing the development of improved cultivars with desirable traits such as drought and disease tolerance, better starch quality and yield. Therefore, the assessment of diversity in cassava germplasm maintained by farmers is important for maintaining biodiversity and crop improvement. Herein, we report genetic diversity relationships of 52 farmer-preferred cassava landraces from the eastern zone of Tanzania based on morphological descriptors and single nucleotide polymorphisms (SNPs). Cluster analysis was performed for both morphological traits (genetic distance 1.18–0.15) and SNPs (genetic distance 0.078–0.002). The analysis revealed that there were a total of 17,393 variant positions, and that several of the SNPs were distributed across all the chromosomes. The abundance of SNP varied remarkably among the 18 cassava chromosomes, with chromosome 2 having the highest number of SNPs (1335) and chromosome 18 having the lowest number of SNPs (734). The power of SNPs in distinguishing morphologically similar landraces was shown. Both analyses did not group landraces according to geographical locations, suggesting that farmers were moving cassava germplasm to different areas. Their diversity was mainly due to adaptation and preferential selection by farmers. This further implied that within a geographical location, the cultivars were more diverse and there was no misnaming of cassava cultivars by farmers. The collection revealed a wide range of genetic diversity, and represented a valuable resource for trait improvement, allowing the capture of farmer-preferred traits in future cassava breeding programmes.

Purple- and red-fleshed potato cultivars constitute a great source of phenolic compounds, which may promote human health. Since the characterization of potato germplasm is a key step during the breeding process, the classification of high anthocyanin-producing tetraploid genotypes may facilitate the incorporation of phenolic-related traits in a potato breeding programme. A set of 18 high anthocyanin-producing underutilized tetraploid cultivars, which have been previously classified in terms of phytochemical content, have been characterized by both microsatellite markers (simple sequence repeat, SSR) and morphological descriptors. A wide genetic variability was found using 11 highly discriminatory SSR markers. The collection also displayed a large amount of variation for most morphological traits. The neighbour-joining trees defined by SSR markers and morphological descriptors revealed genetic and phenotypic relatedness of the potato genotypes. Despite the complexity of tetrasomic inheritance, high anthocyanin-producing tetraploid cultivars should be considered for potato breeding since they are adapted to long-day conditions and do not present undesirable characteristics that are found in native accessions or landraces.

Only a little information is available on the genetic association of basic within-boll yield components of segregating populations. A total of 25 genotypes were evaluated for genetic diversity using SSR markers in 2012; of these, eight diverse genotypes were selected to attempt the generation of five crosses. From the progeny of these five crosses, five F3 populations were developed. Data for within-boll yield components were recorded by taking 30 observations (one observation average of five bolls) from each population, and analysed for genotypic and phenotypic correlations followed by the path coefficient analysis from the genotypic correlation. The highest genotypic correlation was observed between seed cotton yield per locule and number of seeds per boll (ranging from 0.654 to 0.972 for different crosses). Except number of seeds per locule and lint percentage, all the other within-boll yield components had a highly significant positive correlation with seed cotton yield, whereas the former two had a negative correlation. Path coefficient analysis revealed that number of seeds per boll had a maximum direct effect on yield (ranging from 0.776 to 0.895 for different crosses), and also had a relatively high magnitude of the indirect effect via other traits. Differences were observed in the magnitude of correlation coefficients and direct/indirect effects for different populations, but the direction of genetic association always remained the same. The present study showed that number of locules per boll, seed cotton yield per locule, number of seeds per boll and seed cotton yield per boll can be used as efficient selection criteria for the improvement in seed cotton yield.

Landraces are an important resource for crop breeding, due to their resilience and content of quality traits. However, genetic and phenotypic variability needs to be carefully characterized for proper direct and indirect use. In the present study, a multidisciplinary approach was carried out to assess the Italian sweet pepper landrace ‘Friariello’. A total of 18 traditional accessions were compared with five hybrids and two ecotypes with similar fruit typology. Genetic and morpho-agronomic characterization allowed us to distinguish five different group types of ‘Friariello’. Accessions showing two/three lobes at the blossom end of the fruit were found to be the most productive, whereas the genotypes showing one/two lobes at the blossom end were the most homogeneous. A total of 167 volatile organic compounds (VOCs) were identified in the collection analysed. Moreover, of the 37 targeted VOCs, 29 showed significant differences in content among the pepper genotypes studied. Of such VOCs related to main flavours described for pepper in the literature, ten were found to be the major determinants of variability among the derived ‘Friariello’ groups. A slightly negative, albeit not significant, correlation was observed between ascorbic acid (AsA) content and agronomic traits, suggesting a better quality for less productive accessions, but also the possibility to improve yield without significantly reducing the AsA levels. The approach used allowed us to define how the different typologies can be used for different breeding purposes, integrating the peculiar properties in order to establish a desirable landrace ideotype. Furthermore, valuable sources for improving quality traits in pepper breeding were identified.

The study of unknown and therefore unexploited genetic material from landraces and wild relatives could be essential to help modern plant breeders to respond to ongoing requirements and new challenges in food production. The present study evaluates the most relevant physicochemical values and nutrient contents of a genetically unique array of traditional melon varieties, cultivated in Spain at least since the 19th century, and compares them with modern melon hybrids available on the market. This research is complemented with an assessment of variety, environment and repetition effects on each trait to determine their stability. Spanish melon landraces displayed extraordinary diversity with respect to juiciness (70.59–95.97 g/100 g water fresh weight), firmness (20.75–149.89 N), soluble solids content (9.57–16.53 °Brix), pH (5.04–6.38), total sugars (360.21–877.36 mg/g dry weight), carotenoids (0.01–2.05 μg/g fresh weight) and ascorbic acid values (7.55–44.33 mg/100 g fresh weight). A subset of these landraces, belonging to Piel de Sapo and Rochet market classes, revealed remarkably superior values of ascorbic acid in comparison with all commercial varieties, doubling ascorbic acid values with respect to their corresponding market class. Furthermore, most of these landraces exhibited high acidity and accumulated high levels of sugars, fulfilling those sensory and physicochemical characteristics that researchers and breeders have spent many years seeking. The possibilities of these landraces to be used in improvement projects are innumerable; they should be surely taken into account in the near future.

Water deficit is an environmental factor that constrains crops to express their ecophysiological potential and causes crop yield reduction. Eruca vesicaria has been reported to be one of the most drought-tolerant species in Cruciferae. In this study, polyethylene glycol-simulated drought tolerance was evaluated in one line of Brassica carinata, one line of Brassica napus and 249 Eruca lines based on the principal component analysis (PCA) and unweighted pair-group arithmetic average (UPGMA) cluster analysis. The PCA based on eight drought tolerance indices indicated that the first three components accounted for 85.46% of the total variation, with principal component (PC) 1 accounting for 43.89%, PC2 for 27.85% and PC3 for 13.73% of the total variation. The UPGMA cluster analysis indicated that B. napus cultivar Zhongshuang 9 and Eruca lines could be clustered into five major groups, with group 1 being, in general, drought sensitive, group 2 being slightly–medium drought tolerant, group 3 being drought tolerant, group 4 being highly drought sensitive and group 5 being highly drought tolerant. B. carinata cultivar XB1, as an outstander, showed high drought sensitivity. The UPGMA cluster dendrogram provides a good representation of the similarity matrix (r= 0.68). The drought-tolerant Eruca materials obtained in this study will be valuable for genetic improvement not only in Eruca itself, but also in Brassica crops since they are drought-tolerant lines from a drought-tolerant species.